Rainbow Electronics AT91CAP9S250A - Manual (Page 766)

766
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
Figure 41-7. Command/Response Functional Flow Diagram
Note: 1. If the command is SEND_OP_COND, the CRC error flag is always present (refer to R3 response in the MultiMedia Card
specification).
41.8.1 Data Transfer Operation
The MultiMedia Card allows several read/write operations (single block, multiple blocks,
stream, etc.). These kind of transfers can be selected setting the Transfer Type (TRTYP) field
in the MCI Command Register (MCI_CMDR).
These operations can be done using the features of the Peripheral DMA Controller (PDC). If
the PDCMODE bit is set in MCI_MR, then all reads and writes use the PDC facilities.
In all cases, the block length (BLKLEN field) must be defined either in the mode register
MCI_MR, or in the Block Register MCI_BLKR. This field determines the size of the data block.
Enabling PDC Force Byte Transfer (PDCFBYTE bit in the MCI_MR) allows the PDC to man-
age with internal byte transfers, so that transfer of blocks with a size different from modulo 4
can be supported. When PDC Force Byte Transfer is disabled, the PDC type of transfers are
in words, otherwise the type of transfers are in bytes.
RETURN OK
RETURN ERROR
(1)
Set the command argument
MCI_ARGR = Argument (1)
Set the command
MCI_CMDR = Command
Read MCI_SR
CMDRDY
Status error flags?
Read response if required
Yes
Wait for command
ready status flag
Check error bits in the
status register (1)
0
1